Erythrocyte Adenosine A2B Receptor-Mediated AMPK Activation: A Missing Component Counteracting CKD by Promoting Oxygen Delivery.

Background: Oxygen deprivation or hypoxia in the kidney drives CKD and contributes to end organ damage. The erythrocyte's role in delivery of oxygen (O) is regulated by hypoxia, but the effects of CKD are unknown.

Methods: We screened all of the metabolites in the whole blood of mice infused with angiotensin II (Ang II) at 140 ng/kg per minute up to 14 days to simulate CKD and compared their metabolites with those from untreated mice. Mice lacking a receptor on their erythrocytes called ADORA2B, which increases O delivery, and patients with CKD were studied to assess the role of ADORA2B-mediated O delivery in CKD.

Results: Untargeted metabolomics showed increased production of 2,3-biphosphoglycerate (2,3-BPG), an erythrocyte-specific metabolite promoting O delivery, in mice given Ang II to induce CKD. Genetic studies in mice revealed that erythrocyte ADORA2B signaling leads to AMPK-stimulated activation of BPG mutase, promoting 2,3-BPG production and O delivery to counteract kidney hypoxia, tissue damage, and disease progression in Ang II-induced CKD. Enhancing AMPK activation in mice offset kidney hypoxia by triggering 2,3-BPG production and O delivery. Patients with CKD had higher 2,3-BPG levels, AMPK activity, and O delivery in their erythrocytes compared with controls. Changes were proportional to disease severity, suggesting a protective effect.

Conclusions: Mouse and human evidence reveals that ADORA2B-AMPK signaling cascade-induced 2,3-BPG production promotes O delivery by erythrocytes to counteract kidney hypoxia and progression of CKD. These findings pave a way to novel therapeutic avenues in CKD targeting this pathway.